The RGBI element doesn't exist in Kiosc but you can easily have a color picker and put a normal fader close by to control the intensity.
I guess your DMX fixtures are connected to the Cuecore3.
If the DMX charts of the fixture already include an intensity channel than you just need to create an action for your intensity fader on kiosc ( using OSC, UDP or TCP) and create a DMX task that will just control the right channel.
If there is no DMX channel for intensity, then you first need to patch your fixtures in the patch tab, and for each fixture activate the "virtual dimmer" function.
Now in the show control create the same action than previously, but this time use a "device" task, and select intensity control.
enjoy